Recently, a protocol of wireless communication system referred to as 3G (3rd generation) is widely employed.
There are some development stages in this 3G, and in addition to the original 3G employed in FOMA and the like, there appears a cellular telephone employing a protocol referred to as 3.5G or HSDPA in which speed of communication is more enhanced. Moreover, now a protocol referred to as Super3G or 3.9G is examined.
A protocol in a wireless communication system of this 3G group is divided into plural layers. A layer 1 among them is a layer referred to as a physical layer and handles actual communication.
FIG. 1 is a protocol block diagram of a layer 2.
The layer 2 positioned on the layer 1 includes three sub layers of a MAC (Medium Access Control), a RLC (Radio Link Control), and a PDCP (Packet Data Convergence Protocol).
Here, a whole of one processing function arranged in one layer or one sub layer is called an entity. PDCP entity or RLC entity exists as many as LCH (Logical Channel) to be used (n pieces of #1˜#n in the example illustrated in FIG. 1). Each PDCP and each RLC correspond to each LCH and transfer a PDU (Protocol Data Unit). Here, the PDCP entity processes concealment of data and the like in 3.9G (Super3G), and the RLC entity processes retransmission control of data and the like.
A MAC entity integrates PDU's transferred from each RLC entity via each LCH into one PDU and transmits the PDU to a HARQ (Hybrid Automatic Repeat reQuest). The HARQ transfers the PDU to the lower layer 1 via a TRCH (Transport Channel).
On a receiving side, the MAC entity divides the PDU transferred from the layer 1 via the TRCH into one PDU or plural PDU's, and transfers the divided PDU's (PDU) to each RLC entity via each LCH.
Incidentally, although there is a layer 3 on the layer 2, the layer 3 is not directly related here so that its illustration and explanation are omitted.
Here, for each PDU, a mechanism capable of exchanging information with a counterpart side by adding not only user data but also control information necessary for an entity on the counterpart side is examined in 3GPP (3rd Generation Partnership Project).
FIG. 2 illustrates an example of a data flow of a PDU with control information added thereto.
In the RLC entity, a header H is added to a RLC-SDU (Source Data Unit) received from the PDCP entity of the same LCH to be transmitted to the MAC entity as a PDU in a RLC sub layer (RLC-PDU). In the MAC entity, RLC-PDU's transmitted from RLC entities of plural LCH's are received as SDU's (MAC-SDU's) in the MAC sub layers. The plural MAC-SDU's are integrated, added with MAC control information and further added with a header H, and transmitted to the layer 1 as one single MAC-PDU. In the layer 1, the MAC-PDU transmitted from the MAC sub layer is transmitted by wireless.
On the other hand, on the receiving side, the MAC-PDU received in the layer 1 is passed to the MAC entity, and in the MAC entity, the received MAC-PDU is divided into MAC-SDU's for each LCH and passed to the RLC entities of each LCH.
Incidentally, in this FIG. 2, a case of normally being transmitted and received is exemplified. Incidentally, the HARQ (see FIG. 1) included in the MAC entity checks whether reception is normal or abnormal by a CRC (Cyclic Redundancy Check), and transmits an ACK (Acknowledgment) toward a transmitting origin if reception is normal (CRC-OK) or transmits a NACK (Negative Acknowledgment) when reception is abnormal (CRC-NG), so that a retransmission request is performed.
FIG. 3 illustrates a data flow including returning of the ACK and NACK by the HARQ on the receiving side.
Here, a case is illustrated in which a HARQ transmission controlling section on the transmitting side operates, and two MAC-PDU's of a MAC-PDU #1 and a MAC-PDU #2 are transmitted toward the receiving side. On the receiving side, these two MAC-PDU's are received, and a HARQ reception controlling section on the receiving side performs a CRC check for each of the received MAC-PDU's. As a result of the CRC check, it is determined that the MAC-PDU #1 is abnormal in receiving (CRC-NG), and a NACK is transmitted toward the transmitting side at this time. When the HARQ transmission controlling section on the transmitting side receives the NACK, the HARQ transmission controlling section performs retransmission control of the same MAC-PDU #1. On the transmitting side, a time when the MAC-PDU #1 is transmitted is managed, and when the NACK is received, it is possible to identify retransmission of which particular MAC-PDU the NACK requests, from a received time of the NACK. Therefore, on the receiving side of the MAC-PDU, simply by transmitting the NACK, without transmitting an identifier of a MAC-PDU in which an abnormality in receiving occurs on the receiving side, it is possible to recognize in which particular MAC-PDU the abnormality in receiving occurs on the transmitting side.
As for the MAC-PDU #2 that is transmitted following the MAC-PDU #1 from the transmitting side, when reception is normal (CRC-OK), the HARQ reception controlling section passes the MAC-PDU #2 to the MAC-PDU determination processing section and also transmits an ACK toward the transmitting side. The transmitting side which receives the ACK recognizes that retransmission control for the MAC-PDU #2 is unnecessary and transmits a MAC-PDU (here, MAC-PDU #n) to be transmitted next.
In the MAC-PDU determination processing section, it is determined whether the MAC-PDU #2 received from the HARQ reception controlling section is a PDU in a normal format or a PDU in an incorrect format.
FIG. 4 is a schematic diagram illustrating a determination processing whether a PDU is in a normal format or an incorrect format in the MAC-PDU determination processing section.
As described above, when the HARQ reception controlling section determines that the reception is normal as a result of the CRC check, the HARQ reception controlling section transmits an ACK toward the transmitting side and also passes the MAC-PDU to the MAC-PDU determination processing section. When the MAC-PDU determination processing section receives the MAC-PDU from the HARQ reception controlling section, it is determined whether the format of the MAC-PDU is normal or incorrect.
For example, the following cases are considered as an incorrect format.
(1) An identifier of a LCH is out of range.
(2) More headers than specified in exist (E (Extension) flag in a header is ON).
(3) A sum of Length information in a header is longer than a received MAC-PDU.
(4) An identifier of the MAC control information is out of range.
(5) An identifier of the MAC control information is different from the Length.
In the MAC-PDU determination processing section, it is determined whether the MAC-PDU is in a normal format or an incorrect format, and when it is determined to be the normal format, the MAC-PDU is divided into MAC-SDU's for each LCH to be passed to a RLC entity of each LCH (see FIG. 2), and when it is determined to be the incorrect format, the MAC-PDU is discarded. In this case, the retransmission control is not performed in the MAC entity. As described above, since the retransmission control is performed in the RLC entity, if the RLC-PDU to be received by the RLC entity is not received, the retransmission request is performed from the RLC entity. However, since there is a condition for performing the retransmission control in the RLC entity, the retransmission control is not performed immediately.
Subsequently, as a technique related to the present invention, an outline of MIMO (Multiple-Input Multiple-Output) to perform communication by using plural antennas will be explained.
FIG. 5 is a block diagram illustrating an outline of a transmitting apparatus and a receiving apparatus employing the MIMO, and FIG. 6 illustrates a data flow when the MIMO is employed.
In a MAC-PDU generation processing section 11 on the transmitting side, RLC-PDU's (MAC-SDU's) received from each RLC are integrated to generate a MAC-PDU as illustrated in FIG. 2. Although this MAC-PDU is generated in multiple numbers depending on generation of data to be transmitted, in FIG. 5 and FIG. 6, two MAC-PDU's of the MAC-PDU #1 and the MAC-PDU #2 are typically illustrated. The MAC-PDU's generated in the MAC-PDU generation processing section 11 are inputted into a layer 1 transmission processing section 13 via the HARQ transmission controlling section 12, the MAC-PDU's are allocated to plural antennas 14a, 14b (here, two antennas as one example), respectively, and transmitted while being shared by these two antennas 14a, 14b. 
On the receiving side, the MAC-PDU's transmitted from these two antennas 14a, 14b on the transmitting side are received by two antennas 24a, 24b, and passed to a layer 1 reception processing section 23. In FIG. 6, a pair of the antennas for transmitting and receiving is referred to as a MIMO antenna while identifying each as a MIMO antenna &1 and a MIMO antenna &2.
The MAC-PDU's received via the plural antennas 24a, 24b in the layer 1 reception processing section 22 on the receiving side are, after a CRC check is performed and a NACK and an ACK are transmitted by the HARQ reception controlling section 22, to be transmitted to the MAC-PDU determination processing section 21. In the MAC-PDU determination processing section 21, the normality or incorrectness of the format is determined, and when determined to be the normal format, the MAC-PDU's are divided into MAC-PDU's for each LCH to be passed to each RLC entity. A MAC-PDU in the incorrect format is discarded in the MAC-PDU determination processing section 21.
Thus, the MIMO is a technique of transmitting and receiving in parallel by using plural antennas, and enables high speed communication since the plural antennas are used so that the bandwidth is widened.
In the above-described communication algorithm, the MAC-PDU determination processing section on the receiving side determines whether a format of the received MAC-PDU is normal or incorrect and when determined to be the incorrect format, the MAC-PDU determination processing section discards the MAC-PDU. Although the acquisition of the discarded data is handled by the retransmission control in the RLC entity, as described above, the retransmission control in the RLC entity is not immediately performed, but it takes some time before the request of retransmission so that a throughput as a whole may decrease.